砂砾岩弹性试验研究

Experimental investigation on elasticity of glutenite

对济阳坳陷东营北带东段地区砂砾岩体储层取样进行岩石物理试验测试。首先利用等效介质理论计算岩石基质的弹性模量;通过薄片观察和弹性模量测试,研究砂砾岩Biot系数变化特征,分不同岩性利用曲线回归干岩样的Biot系数与φ/φc(φ和φc分别为岩石孔隙度和临界孔隙度)关系式模型,根据扩展的Biot-Gassmann关系式计算出流体饱和后的岩石弹性模量,将预测纵横波波速与实际测试进行对比;最后通过岩石物理试验测试,验证Biot-Gas-smann理论用于分析砂砾岩弹性特征的适用性。结果表明:利用HS边界模型计算的弹性模量更接近岩心的实际基质弹性模量,比取经验值精确,且降低了岩样流体饱和后的敏感性影响;Biot系数反映岩石孔隙的刚度,孔隙度大的系数大,它随着有效压力的增大而减小,与岩石的岩性、矿物组成、内部结构有关;利用扩展Biot-Gassmann理论预测纵横波速度得到满意结果,简化了估算纵横波速度的过程。

The samples of rock were obtained from glutenite reservoir area of the Eastern Dongying north zone,Jiyang Depression. The elastic properties of rock were measured. First,the elastic moduli of rock matrix were calculated using effective medium theory. Through rock thin section analysis and elastic moduli test,the variation characteristics about Biot,s coefficient of glutenite were studied. The relationship between dry rock Biot,s coefficient and φ/φc（ φ and φc are rock porosity and critical porosity respectively） were established by the way of nonlinear regression according to different lithologies. The elastic moduli and wave velocities of rock saturated by fluid were calculated by the extended Biot-Gassmann model. The predicted compressional and shear wave velocities were compared with those velocities measured in laboratory. The Biot-Gassmann theory can be applied to analyze the elastic characteristics of glutenite. The results show that the elastic moduli of core matrix calculated by HS boundary model are more accurate than empirical value and reduce the effect of saturated fluid on the elastic moduli. Biot,s coefficient describes the stiffness of the rock pores and relates to the lithology,mineral composition, and internal structure. It increases with porosity increasing and decreases with effective pressure increasing. The compressional wave and shear wave velocities predicted by the extended Biot-Gassmann theory agree well with the velocities measured in laboratory. The process of prediction is also simplified.